High-pressure amphibolite-facies metamorphism and deformation within the Yukon-Tanana and Taylor Mountain terranes, eastern Alaska

Ductilely deformed amphibolite-facies tectonites comprise two adjacent terranes in the eastern part of the Yukon-Tanana upland in eastern Alaska. These terranes differ in protoliths, structural level, and cooling ages. The northern, structurally higher Taylor Mountain terrane includes garnet amphibolite, biotite ± hornblende gneiss, marble, quartzite, metachert, pelitic schist, and crosscutting granitoids of intermediate composition. The southern structurally lower Lake George subterrane of the Yukon-Tanana terrane is made up of quartz-biotite schist and gneiss, augen gneiss, pelitic schist, garnet amphibolite, and quarzite; it is interpreted to comprise a continental margin and granitoid belt built on North American crust. The pressure, temperature, kinematic, and age data indicatethat metamorphism of two terranes took place during different phases of a latest Paleozoic through early Mesozoic shortening episode, resulting from closure of an ocean basin now represented by klippen of the Seventymile-Slide Mountain terrane. -from Authors